The purpose of this CIDA application is to allow me to take advantage of a superb research training environment in which I can continue to acquire experience and credentials to become an independent clinical investigator and pursue basic research into the cellular and molecular mechanisms of transfusion reactions. Hemolytic transfusion reactions (HTR) are one of the most feared adverse consequences of blood transfusion. Our knowledge of the pathophysiologic mechanisms involved in these reactions is incom- plete. In particular, little is known about the role of inflammatory mediators such as cytokines in HTR. To investigate this, I have developed three in vitro models of HTR. Preliminary data using these models indicate that major inflammatory cytokines [tumor necrosis factor-beta(TNF), interleukin-1beta (IL-1), and interleukin-6 (IL-6)]; as well as chemotactic/activating cytokines [monocyte chemoattractant protein-1 (MCP), and interleukin-8 (IL-8)]; and the regulatory cytokine interleukin-1 receptor antagonist (IL-1ra) are produced in response to red cell incompatibility. I propose a set of related experiments to further characterize the cellular and immunologic mechanisms involved in cytokine production induced by red cell incompatibility. Using blocking antibodies, the regulation and interrelationships of elaborated cytokines will be investigated. In addition, the relative contribution of monocytes, macrophages and Kupffer cell-derived cytokines to HTR will be assessed. Finally, the effect of elaborated cytokines on endothelial cell surface adhesion and anticoagulant properties will be studied. These studies will likely lead to a new understanding of the pathophysiologic mechanisms underlying HTR, and suggest specific treatment modalities.